I swapped my d16z6 out at 253k miles because I threw a rod out of the crankcase. So the new motor I bought was a d15B VTEC.. bassically the "mini-me" motor. The problem is, I have a big vacuum leak now? I noticed there is a sensor on my intake manifold (on the driver side, at the top, on the firewall side of the intake) that this japanese motor doesn't have. It connects a small vacuum hose from the charcoal canister to the little sensor and the other side of the sensor goes into the intake manifold below the sensor. I've done whatever I can to try to make this little sensor work without drilling into my new intake manifold. So my new question is.. this is a big vaccum leak. I'm talking idling from 750ish to 1500 and just keeps jumping up and down. It's impossible to tell right now, because the tach sensor isn't hooked up yet, but it's a huge jump. Do you guys really think this tiny little guy would cause all that? or should I be checking other hoses too before I spend my money and time dicking with the little sensor?

Does anyone else have any problems with the japaese motor going into a car made in canada?

and the next question I have is.. should I just put my old intake manifold back on? It has 253,000 hard miles on it. I mean it was driven hard. Some punk kid beat the crap out of it and I did too because I knew I was gonna need a swap. Or would it still be good with a good cleaning and new gaskets? I'm reluctant to do it because the old motor was running a little rich when it VTEC'd, and I don't really want to deal with cleaning out the carbon build up.. plus I'd have to swap fuel rails and all the other crap.

and my third question is: should I invest in an aftermarket intake manifold, and if so, from what company? I have never seen big gains from swapping out.. even on bigger motors like the prelude and accord. What do you guys think?